| 摘要 |
<p>1. Method for the transmission of signals of fixed frequencies, especially teletypewriter signals, in which useful messages are transmitted in consecutive series of dual-time T1 and T2 cycles and in which the received signals are detected by means of detection devices, highly selective for the transmitted frequencies, each of these detection devices providing an output signal with amplitude increasing from zero, beginning with the instant when the excitation of its input with a signal of the frequency to which the said filter is tuned begins, characterized in that a sequence of synchronization signals composed of a certain number of alternations of transmissions of a frequency f1 for a time T1 followed by a frequency f2 for a time T2 is made to precede the transmission of a useful message, in that on the receiving end, a detection device (F1 ) tuned to the frequency f1 is kept enabled during latent periods, in that after the detection of a signal of frequency f1 of predetermined amplitude, the detection device (F1 ) is disabled and a detection device (F2 ) tuned to the frequency f2 is enabled for a time greater than the duration of the time T1 and less than the duration of the sum of the times T1 + T2 , in that the disabling and enabling of the detection devices (F1 F2 ) is then controlled approximately at the rate of the durations of the times T1 and T2 , in that the instants of appearance of maxima of the output signals of the detection devices (F1 and F2 ) are determined in a microprocessor M, in that the mean instants of appearance of the maxima are calculated and in that the change of phase between the times T1 and times T2 are made to coincide with the said mean instants of appearance of the maxima in order to interpret the received frequencies (f1 to f8 ) representing the useful message.</p> |
